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• select all values from a dimension for which there are facts in all other dimensions

  - by ideasculptor

  I've tried to simplify for the purposes of asking this question. Hopefully, this will be comprehensible. Basically, I have a fact table with a time dimension, another dimension, and a hierarchical dimension. For the purposes of the question, let's assume the hierarchical dimension is zip code and state. The other dimension is just descriptive. Let's call it 'customer' Let's assume there are 50 customers. I need to find the set of states for which there is at least one zip code in which EVERY customer has at least one fact row for each day in the time dimension. If a zip code has only 49 customers, I don't care about it. If even one of the 50 customers doesn't have a value for even 1 day in a zip code, I don't care about it. Finally, I also need to know which zip codes qualified the state for selection. Note, there is no requirement that every zip code have a full data set - only that at least one zip code does. I don't mind making multiple queries and doing some processing on the client side. This is a dataset that only needs to be generated once per day and can be cached. I don't even see a particularly clean way to do it with multiple queries short of simply brute-force iteration, and there are a heck of a lot of 'zip codes' in the data set (not actually zip codes, but the there are approximately 100,000 entries in the lower level of the hierarchy and several hundred in the top level, so zipcode-state is a reasonable analogy)

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• How do I create a class repository in Java and do I really need it?

  - by Roman

  I have a large number of objects which are identified by names (strings). So, I would like to have a kind of mapping from object name to the class instances. I was told that in this situation I can use a "repository" class which works like that: Server myServer = ServerRepository.getServer("NameOfServer"); So, if there is already an object (sever) with the "NameOfServer" it will be returned by the "getServer". If such an object does not exist yet, it will be created and returned by the "getServer". So, my question is how to program such a "repository" class? In this class I have to be able to check if there is an instance of a given class such that it has a given value of a given field. How can I do it? I need to have a kind of loop over all existing object of a given class? Another part of my question is why I cannot use associative arrays (associative container, map, mapping, dictionary, finite map)? (I am not sure how do you call it in Java) In more details, I have an "array" which maps names of objects to objects. So, whenever I create a new object, I add a new element to the array: myArray["NameOfServer"] = new Server("NameOfServer").

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• Add xml-stylesheet and get standalone = yes.

  - by tumba25

  The code at the bottom is what I have. I removed the creation of all tags. At the top in the xml file I get.<?xml version="1.0" encoding="UTF-8" standalone="no"?> Note that standalone is no, even thou I have it set to yes. The first question: How do I get standalone = yes? I would like to add <?xml-stylesheet type="text/xsl" href="my.stylesheet.xsl"?> at line two in the xml file. Second question: How do I do that? Some useful links? Anything? DocumentBuilderFactory dbfac = DocumentBuilderFactory.newInstance(); DocumentBuilder docBuilder = dbfac.newDocumentBuilder(); Document doc = docBuilder.newDocument(); <cut> TransformerFactory transfac = TransformerFactory.newInstance(); transfac.setAttribute("indent-number", new Integer(2)); Transformer trans = transfac.newTransformer(); trans.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); trans.setOutputProperty(OutputKeys.STANDALONE, "yes"); trans.setOutputProperty(OutputKeys.INDENT, "yes"); trans.setOutputProperty(OutputKeys.CDATA_SECTION_ELEMENTS, "name"); FileOutputStream fout = new FileOutputStream(filepath); BufferedOutputStream bout= new BufferedOutputStream(fout); trans.transform(new DOMSource(doc), new StreamResult(new OutputStreamWriter(bout, "utf-8")));

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• Attempted to render a circle in opengl es 1.1, renders as oval

  - by eipxen

  Hi all, I attempted to render a circle in opengl es 1.1 as a test before building a larger program, but it renders as an oval. Here is the code I use to generate and render my vertices: static const int numVerts = 40; static GLfloat myFirstCircle[82]; myFirstCircle[0] = 0.0f; myFirstCircle[1] = 0.0f; for (int i = 2; i < (numVerts+1)*2; i+=2) { myFirstCircle[i] = .5 * cosf(i*2*3.14159/numVerts); myFirstCircle[i+1] = .5 * sinf(i*2*3.14159/numVerts); } glVertexPointer(2, GL_FLOAT, 0, myFirstCircle); glEnableClientState(GL_VERTEX_ARRAY); glDrawArrays(GL_TRIANGLE_FAN, 0, 22); I'm still somewhat new to this system, so I may have a silly error that I do not see, but it seems to me like this should generate 40 vertices on a circle of radius .5. When it renders, the shape on screen appears to be an oval, significantly taller than it is wide. My question is thus: why is my circle rendering this way, and what could I do to fix it? This is the first question on stackoverflow, so I'm not sure how to share an image of my output.

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• Why does C# not provide the C++ style 'friend' keyword?

  - by Ash

  The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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• Java if statement strings and more

  - by user1820578

  I have decided to try and learn a little in java tonight and i have just been trying some stuff with things i have learned. My question is in an if statement how to i make two stings to be true. Here is what i have so far. if ("male".equals(gender)) && ("brendan".equals(name)) the problem i am pretty sure is the && but i am not sure. also my other question is with gender it should either be male or female. I want to have if statement with male and another for female. For this do i just do another if. For eg if ("male".equals(gender)) && ("brendan".equals(name)) { System.out.println("blah blah"); } else { System.out.println(" wrong wrong"); } if ("female".equals(gender)) { System.out.println("blah blah2"); } else { System.out.println(" wrong wrong 2"); } hope that makes sense. Any help would be great.

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• Why can't I display a unicode character in the Python Interpreter on Mac OS X Terminal.app?

  - by apphacker

  If I try to paste a unicode character such as the middle dot: · in my python interpreter it does nothing. I'm using Terminal.app on Mac OS X and when I'm simply in in bash I have no trouble: :~$ · But in the interpreter: :~$ python Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> ^^ I get nothing, it just ignores that I just pasted the character. If I use the escape \xNN\xNN representation of the middle dot '\xc2\xb7', and try to convert to unicode, trying to show the dot causes the interpreter to throw an error: >>> unicode('\xc2\xb7') Traceback (most recent call last): File "<stdin>", line 1, in <module> UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 0: ordinal not in range(128) I have setup 'utf-8' as my default encoding in sitecustomize.py so: >>> sys.getdefaultencoding() 'utf-8' What gives? It's not the Terminal. It's not Python, what am I doing wrong?! This question is not related to this question, as that indivdiual is able to paste unicode into his Terminal.

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• Is it possible to filter data used by pivot table based on filtering the rows in a source table in Excel?

  - by Geoffrey Stoel

  I have developed a dashboard in Excel 2007 that uses one source table in a sheet (being filled with a query on our data warehouse) and multiple pivot tables making different cross sections on this data. I use the GETPIVOTDATA in almost a hundred formulas to give me the right value for a specific indicator in my dashboard. This all works fine. However I now have received the question to make the dashboard for 5 different segments. As you can imagine I don't want to create 5 different workbooks for this and need to maintain the dashboard logic on all of them. So my question is the following. Is it possible to automatically (through VBA or any other means) filter the results in my source table which is the source for my pivot tables and thus for my dashboard values. So schematically: DATABASE_VIEW -- SOURCE_TABLE -- 12 pivot tables -- 100 GETPIVOTDATA functions Preferably I would like to load all the segments in the source_table (one view on my database) and then filter the data in the source table, which results in filterd source_dat for my pivots. This way I can (without requerying the db) quickly change between segments in the dashboards (refreshing pivots only). Data in the source table has the column: CUSTOMER_SEGMENT available to filter upon. Any help is appreciated. Geoffrey

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• R plotting multiple histograms on single plot to .pdf as a part of R batch script

  - by Bryce Thomas

  I am writing R scripts which play just a small role in a chain of commands I am executing from a terminal. Basically, I do much of my data manipulation in a Python script and then pipe the output to my R script for plotting. So, from the terminal I execute commands which look something like $python whatever.py | R CMD BATCH do_some_plotting.R. This workflow has been working well for me so far, though I have now reached a point where I want to overlay multiple histograms on the same plot, inspired by this answer to another user's question on Stackoverflow. Inside my R script, my plotting code looks like this: pdf("my_output.pdf") plot(hist(d$original,breaks="FD",prob=TRUE), col=rgb(0,0,1,1/4),xlim=c(0,4000),main="original - This plot is in beta") plot(hist(d$minus_thirty_minutes,breaks="FD",prob=TRUE), col=rgb(1,0,0,1/4),add=T,xlim=c(0,4000),main="minus_thirty_minutes - This plot is in beta") Notably, I am using add=T, which is presumably meant to specify that the second plot should be overlaid on top of the first. When my script has finished, the result I am getting is not two histograms overlaid on top of each other, but rather a 3-page PDF whose 3 individual plots contain the titles: i) Histogram of d$original ii) original - This plot is in beta iii) Histogram of d$minus_thirty_minutes So there's two points here I'm looking to clarify. Firstly, even if the plots weren't overlaid, I would expect just a 2-page PDF, not a 3-page PDF. Can someone explain why I am getting a 3-page PDF? Secondly, is there a correction I can make here somewhere to get just the two histograms plotted, and both of them on the same plot (i.e. 1-page PDF)? The other Stackoverflow question/answer I linked to in the first paragraph did mention that alpha-blending isn't supported on all devices, and so I'm curious whether this has anything to do with it. Either way, it would be good to know if there is a R-based solution to my problem or whether I'm going to have to pipe my data into a different language/plotting engine.

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• After Delete Trigger Fires Only After Delete?

  - by Brandi

  I thought "after delete" meant that the trigger is not fired until after the delete has already taken place, but here is my situation... I made 3, nearly identical SQL CLR after delete triggers in C#, which worked beautifully for about a month. Suddenly, one of the three stopped working while an automated delete tool was run on it. By stopped working, I mean, records could not be deleted from the table via client software. Disabling the trigger caused deletes to be allowed, but re-enabling it interfered with the ability to delete. So my question is 'how can this be the case?' Is it possible the tool used on it futzed up the memory? It seems like even if the trigger threw an exception, if it is AFTER delete, shouldn't the records be gone? All the trigger looks like is this: ALTER TRIGGER [sysdba].[AccountTrigger] ON [sysdba].[ACCOUNT] AFTER DELETE AS EXTERNAL NAME [SQL_IO].[SQL_IO.WriteFunctions].[AccountTrigger] GO The CLR trigger does one select and one insert into another database. I don't yet know if there are any errors from SQL Server Mgmt Studio, but will update the question after I find out.

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• How to update GUI thread/class from worker thread/class?

  - by user315182

  First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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• MySQL SELECT combining 3 SELECTs INTO 1

  - by Martin Tóth

  Consider following tables in MySQL database: entries: creator_id INT entry TEXT is_expired BOOL other: creator_id INT entry TEXT userdata: creator_id INT name VARCHAR etc... In entries and other, there can be multiple entries by 1 creator. userdata table is read only for me (placed in other database). I'd like to achieve a following SELECT result: +------------+---------+---------+-------+ | creator_id | entries | expired | other | +------------+---------+---------+-------+ | 10951 | 59 | 55 | 39 | | 70887 | 41 | 34 | 108 | | 88309 | 38 | 20 | 102 | | 94732 | 0 | 0 | 86 | ... where entries is equal to SELECT COUNT(entry) FROM entries GROUP BY creator_id, expired is equal to SELECT COUNT(entry) FROM entries WHERE is_expired = 0 GROUP BY creator_id and other is equal to SELECT COUNT(entry) FROM other GROUP BY creator_id. I need this structure because after doing this SELECT, I need to look for user data in the "userdata" table, which I planned to do with INNER JOIN and select desired columns. I solved this problem with selecting "NULL" into column which does not apply for given SELECT: SELECT creator_id, COUNT(any_entry) as entries, COUNT(expired_entry) as expired, COUNT(other_entry) as other FROM ( SELECT creator_id, entry AS any_entry, NULL AS expired_entry, NULL AS other_enry FROM entries UNION SELECT creator_id, NULL AS any_entry, entry AS expired_entry, NULL AS other_enry FROM entries WHERE is_expired = 1 UNION SELECT creator_id, NULL AS any_entry, NULL AS expired_entry, entry AS other_enry FROM other ) AS tTemp GROUP BY creator_id ORDER BY entries DESC, expired DESC, other DESC ; I've left out the INNER JOIN and selecting other columns from userdata table on purpose (my question being about combining 3 SELECTs into 1). Is my idea valid? = Am I trying to use the right "construction" for this? Are these kind of SELECTs possible without creating an "empty" column? (some kind of JOIN) Should I do it "outside the DB": make 3 SELECTs, make some order in it (let's say python lists/dicts) and then do the additional SELECTs for userdata? Solution for a similar question does not return rows where entries and expired are 0. Thank you for your time.

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• Learning libraries without books or tutorials

  - by Kawili-wili

  While many ask questions about where to find good books or tutorials, I'd like to take the opposite tack. I consider myself to be an entry-level programmer ready to move up to mid-level. I have written code in c, c++, c#, perl, python, clojure, vb, and java, so I'm not completely clueless. Where I see a problem in moving to the next level is learning to make better use of the literally hundreds upon hundreds of libraries available out there. I seem paralyzed unless there is a specific example in a book or tutorial to hand-hold me, yet I often read in various forums where another programmer attempts to assist with a question. He/she will look through the docs or scan the available classes/methods in their favorite IDE and seem to grok what's going on in a relatively short period of time, even if they had no previous experience with that specific library or function. I yearn to break the umbilical chord of constantly spending hour upon hour searching and reading, searching and reading, searching and reading. Many times there is no book or tutorial, or if there is, the discussion glosses over my specific needs or the examples shown are too far off the path for the usage I had in mind or the information is outdated and makes use of deprecated components or the library itself has fallen out of mainstream, yet is still perfectly usable (but no docs, books, or tutorials to hand-hold). My question is: In the absence of books or tutorials, what is the best way to grok new or unfamiliar libraries? I yearn to slicken the grok path so I can get down to the business of doing what I love most -- coding.

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• UITableView superClass for delegate?

  - by fuzzygoat

  A quick question, I am setting a delegate for UITableView and I have a question regarding setting the delegate and dataSource properties. I have noticed that the properties for delegate and dataSource are not available, I was thinking that adopting the protocols would make them available. But I am now thinking that I maybe have the superclass for my delegate class wrong. Currently I have: -(void)viewDidLoad { TestDelegate *tempDelegate = [[TestDelegate alloc] init]; [self setMyDelegate:tempDelegate]; // setDelegate // setDataSource [tempDelegate release]; [super viewDidLoad]; } My interface for TestDelegate looks like: @interface TestDelegate : NSObject <UITableViewDelegate, UITableViewDataSource> { NSArray *listData; int myCounter; } Can I ask if the above should be: @interface TestDelegate : UITableView <UITableViewDelegate, UITableViewDataSource> { NSArray *listData; int myCounter; } gary EDIT: I think it might be right as NSObject, I have a viewtableView in IB, thats what I will need to connect my delegate class to. I added to tableView in IB so maybe I just need to make it available in Xcode.

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• Class library reference problem

  - by Anindya Chatterjee

  I am building a class library and using its default namespace as "System". There suppose I am creating a generic data structure say PriorityQueue and putting it under System.Collections.Generic namespace. Now when I am referencing that library from another project, I can't see PriorityQueue under "System.Collections.Generic" namespace anymore. Though the library is referenced in that project I can not access any of the classes in it. My question was mscorlib and System.dll share similar namespaces, but still classes from both the assembly is accessible, but why can't mine? If I put a public class under System.Collections.Generic namespace in my class library and refer that library in a project and use a statement like "using System.Collections.Generic", still why I can't access my class there? This was an experimentation I did, I know using System namespace is not encouraged in custom class library, but I want to know the reason behind why I can't access my class in this special case? Please someone shed some light on it. PS: Last time I asked similar question but put it wrongly, so people got misunderstood and I didn't get my answer. This time I am trying to put it correctly as far as I can. Sorry for the misunderstanding.

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• InvalidOperationException: The Undo operation encountered a context that is different from what was

  - by McN

  I got the following exception: Exception Type: System.InvalidOperationException Exception Message: The Undo operation encountered a context that is different from what was applied in the corresponding Set operation. The possible cause is that a context was Set on the thread and not reverted(undone). Exception Stack: at System.Threading.SynchronizationContextSwitcher.Undo() at System.Threading.ExecutionContextSwitcher.Undo() at System.Threading.ExecutionContext.runFinallyCode(Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteBackoutCodeHelper(Object backoutCode, Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Net.ContextAwareResult.Complete(IntPtr userToken) at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken) at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) Exception Source: mscorlib Exception TargetSite.Name: Undo Exception HelpLink: The application is a Visual Studio 2005 (.Net 2.0) console application. It is a server for multiple TCP/IP connections, doing asynchronous socket reads and synchronous socket writes. In searching for an answer I came across this post which talks about a call to Application.Doevents() which I don't use in my code. I also found this post which has a resolution involved with Component which I also don't use in my code. The application does reference a library that I created that contains custom user controls and components, but they are not being used by the application. Question: What caused this to happen and how do I prevent this from happening again? Or a more realistic question: What does this exception actually mean? How is "context" defined in this situation? Anything that can help me understand what is going on would be very much appreciated.

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• C - dns query to structure

  - by Bibo

  I have these structures: typedef struct dnsQuery { char header[12]; struct dnsQuerySection *querySection; } TdnsQuery; typedef struct dnsQuerySection { unsigned char *name; struct dnsQueryQuestion *question; } TdnsQuerySection; typedef struct dnsQueryQuestion { unsigned short qtype; unsigned short qclass; } TdnsQueryQuestion; and I have dns query in byte array from recvfrom. I am trying to get structure from byte array like this: TdnsQuery* dnsQuery = (TdnsQuery*)buf; When I tried to access qtype like this: printf("%u", dnsQuery->querySection->question.qtype); I get seg fault 11. Can someone help me with these structures? What´s wrong with them? I tried to add structure: typedef struct udpPacket { char header[8]; structr dnsQuery query; } and mapped this structure from byte array but it didn´t help. Can someone help me with these structures? How they should look like for dns query with udp protocol?

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• Java Executor: Small tasks or big ones?

  - by Arash Shahkar

  Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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• horizontal uiview's controls unresponsive.. or how to foul up a view hierarchy

  - by Oldmicah

  Hello all, I'm working on an app that has two sections, a config section and a results section. My config section needs to be 2 separate views (horizontal and vert, and yes, I can hear the intake of breath from here), with one rotatable view for the results. b/c of layout restraints and a lot of pain around rotation, I'm not using a navigation controller. I've been experiencing the joys of rotation experimentation and have settled upon keeping my views contained as subviews of my view controller. i.e. view controller.view.subviews = configH, configV, and results. I then use the controller.view bringSubviewToFront to bring the either the configH, configV, or the result view to the front. Rotation works-queue(humor intended) the angelic choirs... almost. What's happening is that my configV button's are responsive, but when the device (or simulator) is rotated, my configH controls are not. (configV is the second subview added, but the first one to be brought to the front because app comes up in portrait mode) The controls on the results view also work. Plan B was to assign the controller.view to configH, configV, or results. All of my controls now work, but rotation is now fouled up. Question 1: Is there a better way to do this? (a horizontal and vertical config view and a rotatable results view) Question 2: Does the above suggest a design issue, or is it more likely that my addled brain is just missing something in my own code. (nothing from the peanut gallery please) many thanks!

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• Facebook SSO authorize in safari but not in facebook app

  - by Pedro Calero

  My problem: I has developed an app with Facebook SSO in my iPhone/iPad. It was working OK. But I have changed the certificate of my app (so now it has new app ID). I also have changed the "iOS pack ID" property in Facebook: I deleted the old app ID and I added the new one. But now my app doesn't do the Facebook SSO when Facebook app is installed. It does it OK when Facebook app is not installed and it uses Safari. I have read this question and this question that say the problem is the "iOS pack ID" and app ID don't match. I have checked it a lot of times, and it is the same. I have put the old app ID in the "iOS pack ID" property of Facebook, but it still doesn't work. I don't know if Facebook take a time to check if my app ID is valid, and how they show the result. I have been a lot of time with this issue. It seem like the problem is the iOS pack ID is not exactly the app ID, but it is not the problem: they are exactly the same. Thank you very much.

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• Boost Asio UDP retrieve last packet in socket buffer

  - by Alberto Toglia

  I have been messing around Boost Asio for some days now but I got stuck with this weird behavior. Please let me explain. Computer A is sending continuos udp packets every 500 ms to computer B, computer B desires to read A's packets with it own velocity but only wants A's last packet, obviously the most updated one. It has come to my attention that when I do a: mSocket.receive_from(boost::asio::buffer(mBuffer), mEndPoint); I can get OLD packets that were not processed (almost everytime). Does this make any sense? A friend of mine told me that sockets maintain a buffer of packets and therefore If I read with a lower frequency than the sender this could happen. ¡? So, the first question is how is it possible to receive the last packet and discard the ones I missed? Later I tried using the async example of the Boost documentation but found it did not do what I wanted. http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/tutorial/tutdaytime6.html From what I could tell the async_receive_from should call the method "handle_receive" when a packet arrives, and that works for the first packet after the service was "run". If I wanted to keep listening the port I should call the async_receive_from again in the handle code. right? BUT what I found is that I start an infinite loop, it doesn't wait till the next packet, it just enters "handle_receive" again and again. I'm not doing a server application, a lot of things are going on (its a game), so my second question is, do I have to use threads to use the async receive method properly, is there some example with threads and async receive? Thanks for you attention.

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• Auto increment with a Unit Of Work

  - by Derick

  Context I'm building a persistence layer to abstract different types of databases that I'll be needing. On the relational part I have mySQL, Oracle and PostgreSQL. Let's take the following simplified MySQL tables: CREATE TABLE Contact ( ID varchar(15), NAME varchar(30) ); CREATE TABLE Address ( ID varchar(15), CONTACT_ID varchar(15), NAME varchar(50) ); I use code to generate system specific alpha numeric unique ID's fitting 15 chars in this case. Thus, if I insert a Contact record with it's Addresses I have my generated Contact.ID and Address.CONTACT_IDs before committing. I've created a Unit of Work (amongst others) as per Martin Fowler's patterns to add transaction support. I'm using a key based Identity Map in the UoW to track the changed records in memory. It works like a charm for the scenario above, all pretty standard stuff so far. The question scenario comes in when I have a database that is not under my control and the ID fields are auto-increment (or in Oracle sequences). In this case I do not have the db generated Contact.ID beforehand, so when I create my Address I do not have a value for Address.CONTACT_ID. The transaction has not been started on the DB session since all is kept in the Identity Map in memory. Question: What is a good approach to address this? (Avoiding unnecessary db round trips) Some ideas: Retrieve the last ID: I can do a call to the database to retrieve the last Id like: SELECT Auto_increment FROM information_schema.tables WHERE table_name='Contact'; But this is MySQL specific and probably something similar can be done for the other databases. If do this then would need to do the 1st insert, get the ID and then update the children (Address.CONTACT_IDs) – all in the current transaction context.

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• Is it possible to send OSC commands to an iPad via the Camera Connection Kit?

  - by HELVETICADE

  I'm building a small controller device that I'd like to partner with a computer. I've settled on using OSC out from my custom built hardware and am pretty satisfied with what I can get from WOscLib. Two goals I'd like to achieve are portability and a very nice ratio between battery:computing power, and this has lured me towards using iPhoneOS to accomplish my goals. I think the iPad would suit my needs perfectly, except that using wifi to broadcast OSC out from my device requires that device to be connected to a third device with a wifi chip, and this would destroy the goal of portability, whilst also introducing potential latency and stability headaches. My question is pretty simple: Can I push OSC commands FROM my controller TO an iPad via USB and the Camera Connection Kit? If I could accomplish this, the two major goals of my project would be fulfilled very nicely. This seems like it should be a simple little question, but researching this obsessively over the past few weeks has left me more almost more uncertain than if I had done no research at all. I'd really like some more confidence before I go down this route, and it seems like it should be possible. Any insight would be very, very appreciated.

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• minimum L sum in a mxn matrix - 2

  - by hilal

  Here is my first question about maximum L sum and here is different and hard version of it. Problem : Given a mxn *positive* integer matrix find the minimum L sum from 0th row to the m'th row . L(4 item) likes chess horse move Example : M = 3x3 0 1 2 1 3 2 4 2 1 Possible L moves are : (0 1 2 2), (0 1 3 2) (0 1 4 2) We should go from 0th row to the 3th row with minimum sum I solved this with dynamic-programming and here is my algorithm : 1. Take a mxn another Minimum L Moves Sum array and copy the first row of main matrix. I call it (MLMS) 2. start from first cell and look the up L moves and calculate it 3. insert it in MLMS if it is less than exists value 4. Do step 2. until m'th row 5. Choose the minimum sum in the m'th row Let me explain on my example step by step: M[ 0 ][ 0 ] sum(L1 = (0, 1, 2, 2)) = 5 ; sum(L2 = (0,1,3,2)) = 6; so MLMS[ 0 ][ 1 ] = 6 sum(L3 = (0, 1, 3, 2)) = 6 ; sum(L4 = (0,1,4,2)) = 7; so MLMS[ 2 ][ 1 ] = 6 M[ 0 ][ 1 ] sum(L5 = (1, 0, 1, 4)) = 6; sum(L6 = (1,3,2,4)) = 10; so MLMS[ 2 ][ 2 ] = 6 ... the last MSLS is : 0 1 2 4 3 6 6 6 6 Which means 6 is the minimum L sum that can be reach from 0 to the m. I think it is O(8*(m-1)*n) = O(m*n). Is there any optimal solution or dynamic-programming algorithms fit this problem? Thanks, sorry for long question

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• Java - How to declare table[i][j] elements as instance variables?

  - by JDelage

  All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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